1. For dough: In a food processor, combine flour, sugar and salt. Add butter and process until it looks like coarse crumbs. Add yolk and milk; process until dough just comes together. Dump dough onto 2 large sheets of overlapping plastic wrap. Press into a disk, wrap and chill 30 minutes or overnight.

2. In a saucepan, cook jam and cornstarch mixture over medium heat, stirring, until slightly thickened and bubbly.

3. Line 2 baking sheets with parchment. On a lightly floured surface, divide dough in half; form into rectangles. Roll one out to 16 by 9 inches. Using a ruler and pizza cutter, cut dough into 12 3-by-4-inch rectangles. Set on a baking sheet and chill while you repeat with remaining dough.

Advertisement

4. Lightly brush half the rectangles with beaten egg. Dollop a tablespoon of cooled filling into the center of each. Spread it, leaving a 1/2-inch border. Top with a plain dough rectangle, pressing edges together with your fingertips. Don't let the filling ooze out. Crimp edges with a fork. Put 6 tarts on each baking sheet, and prick the centers all over with the fork. Refrigerate.